1. Field of the Invention
This invention relates to a nozzle touch sprue bushing device to be provided at an introducing and connecting portion for a plastic material such as a synthetic resin provided on an outer frame in a unit-type injection metal mold or the like wherein a molding element body such as the metal mold or the like includes an inner mold element which is removably mounted on the outer frame mounted on an injection molding machine.
2. Description of the Prior Art
In an injection molding machine which injects a molten plastic material at a high temperature and at a high pressure to mold at one stroke, if connection of a material introducing path is incomplete even a little, leakage of resin will take place so that not only articles may fail but also there is the possibility that a danger may be caused in operation. Thus, conventionally the introducing paths of an injecting machine and a molding element are formed as an integral single material introducing path except at a nozzle touch between the injecting machine and the molding element, and contacting connection between the introducing paths cannot be anticipated. However, in order to change the type of articles to be molded, the entire metal mold must be exchanged, which is very uneconomical. Thus, in order to cope with this problem, an improvement has been proposed wherein a metal mold is divided into an inner mold element and an outer frame so that the type of articles to be molded can be changed more easily. In such an arrangement, interconnection between the introducing paths of the inner mold element and the outer frame relies upon the accuracy of a mirror face working of mutually contacting faces of the inner mold element and the outer frame and also upon a positioning and fixing technique depending upon lapping upon fitting of the inner mold element into the outer frame.
In this instance, the steps at which a highest skill is required for contacting connection of the introducing paths are to finish contacting faces of both elements in which the relay introducing paths are provided so that they may have surfaces of a very high accuracy and to position the contacting faces in parallel to each other and contact them closely to each other. If the accuracy in such surface finish is low, this will cause a problem that leakage of a resin material may take place so that unacceptable molded articles may be produced. Incidentally, in molding of a plastic material, molten plastic material is injected at a high pressure of 2,000 kg/cm.sup.2 to 1,500 kg/cm.sup.2 in the case of engineering plastics and of at least 300 kg/cm.sup.2 in the case of plastics for toys and so on which require a very high accuracy.
Further, connection between an introducing path and an injecting path requires much labor and a high technique to make an adjustment at several times by lapping depending upon temporary fastening as positioning when an inner mold element is fitted into an outer frame.